The present invention relates to the medical imaging arts. It particularly relates to helical or multi-slice volumetric cardiac computed tomography (CT) imaging, and will be described with particular reference thereto. However, the invention will also find application in the computed tomographic imaging of other dynamically moving organs, in angiographic imaging, and in medical imaging of dynamically moving organs using other medical imaging techniques such as magnetic resonance imaging (MRI) and nuclear medical imaging.
Cardiac volumetric computed tomography (CT) imaging typically employs an x-ray source that generates a fan-beam, wedge-beam, or cone-beam of x-rays that traverse an examination region within which a patient's heart is disposed. The cardiac tissue, coronary arteries, and blood therewithin interacts with and absorbs a portion of the traversing x-rays. Typically, a contrast agent is administered to the patient to improve blood contrast. A one- or two-dimensional radiation detector arranged opposite the x-ray source detects and measures intensities of the transmitted x-rays.
During scanning the patient is linearly advanced between axial scans to perform multi-slice CT imaging, or the patient is continuously linearly advanced during x-ray source rotation to perform helical CT imaging. The imaging data is reconstructed using a filtered backprojection, a PI reconstruction, or the like to generate volumetric image representations. Preferably, the cardiac cycle is monitored by an electrocardiograph or other device, and the imaging data is binned into cardiac phase bins to reconstruct the heart at a plurality of phases.
A wide range of cardiac studies are performed using cardiac CT. Qualitative review of cardiac CT images by trained medical personnel detects congenital heart defects, large aneurysms or stenoses in the major coronary arteries, and other gross anatomical abnormalities. Analyses such as heart pumping capacity measurements, blood perfusion studies in myocardium, and coronary vessel tracking provide complementary quantitative diagnostic information.
Modern multi-slice and helical CT scanners produce large quantities of data. In a typical cardiac imaging session, a portion of the heart extending about 12 cm along the head-to-foot direction is imaged using approximately 180 axial slices to provide high spatial resolution. The cardiac cycle is typically binned into about 10 cardiac phase bins to provide good temporal resolution, so that 1800 slices are acquired in the cardiac imaging session.
Reconstruction of this plethora of data is time consuming. Moreover, for certain cardiac diagnostic objectives, not all the imaging data is necessary. For qualitative study of congenital heart defects or other gross anatomical features, image reconstructions at only one or two optimal cardiac phases is often sufficient. Similarly, coronary vessel tracking is preferably performed on an image reconstruction at a selected optimal cardiac phase in which the tracked coronary artery is substantially stationary.
Although for certain studies only one or a few optimal cardiac phases are needed, typically all the CT imaging data is reconstructed, and then the optimal cardiac phases are identified from the complete set of reconstructed images. Additionally, for other diagnostic objectives such as ventricular functional analysis, the complete set of reconstructed images is used.
Present CT imaging systems typically include a CT scanner and associated data acquisition and image reconstruction software, which produces a complete set of reconstructed images. The operator performs initial planar survey scans to identify a spatial position of the heart and to optimize other imaging parameters. The contrast agent is then administered, and low-dosage imaging is performed to monitor the contrast agent intake into the heart. When the image contrast due to contrast agent reaches a selected threshold, the operator initiates high resolution diagnostic imaging. Typically, the operator is given little guidance on optimizing the survey, monitoring, and diagnostic imaging steps. Once the diagnostic imaging is complete, the full CT data set is reconstructed.
Once the data is collected and reconstructed, a suitable analysis module is selected from a suite of analysis software modules. Each module in the analysis software suite is independently designed and configured for a specific diagnostic objective. There is typically no communication between the analysis modules, or between the analysis software suite and the data acquisition and reconstruction software components.
This disconnected modular arrangement has a number of disadvantages. Because the modules are substantially separate, common processing elements such as selection of optimal cardiac phases are duplicated.
The disconnected nature of the arrangement provides little guidance to the user in planning and coordinating the cardiac CT imaging session. A significant amount of time and effort is expended in selecting and initiating each step of the session workflow. Because a contrast agent is typically employed in cardiac CT imaging, coordinated timing of the imaging session with the contrast agent intake is important to ensure that contrast-enhanced images comporting with the specific diagnostic objective or objectives are obtained.
For diagnostic objectives where only one or a few cardiac phases are optimally selected, the disconnect between the data acquisition and reconstruction software components and the analyses software suite means that the complete set of images is reconstructed prior to selection of the optimal cardiac phases. This results in substantial unnecessary reconstruction processing.
The present invention contemplates an improved apparatus and method that overcomes the aforementioned limitations and others.